The internal failure of rock samples subjected to pulsed water jet impacts

• The capacity of pulsed water jets in creating internal microstructural failure within rock targets was studied.
• Internal damage was measured as of reduction in shear wave quality factor, Qs.
• Pulsed water jets were found capable of introducing microstructural damage in both marble and granite targets.
• Pulse length and pulsation frequency of the jet were found cooperating in developing internal damage.
• Brittleness and dynamic crack propagation mechanism of the target influenced the efficacy of a pulsed water jet.

The capacity of pulsed water jets for creating internal breakdown within a rock target was the subject of this investigation. The resultant, internal damage is defined as an increase in micro-crack density within the rock samples. It is attributed to the occurrence of a fatigue phenomenon resulting from the periodic impacts of high-velocity water-pulses and from the interaction of the induced stress-waves within the target material. This paper reports an investigation into the extent to which fatigue damage occurred in rocks that were subjected to pulsed, water jet impacts. For this purpose, the wave-attenuation capacity of rock samples, before and after being subjected to a pulsed water jet, was measured and the relative disparity between these two figures was then utilised as a measure of the potency of the pulsed water jets in producing an internal breakdown within the rock targets. The results indicated and confirmed the occurrence of internal damage in tested marble and granite samples. The pulse lengths and the pulsation frequencies of the water jets were found to cooperate in developing the internal damage and, depending on the rock type, one played a more significant role than the other.